The invention relates to a pressure application device for retaining at least two electronic components disposed opposite each other and on each side of the same connection board.
More precisely, the invention relates to a device comprising:
two rigid bearing plates disposed on each side of the connection board, said plates exert a retaining force by pressure on said electronic components in the direction of the connection board, and
first fixing or clamping means for fixing or clamping the bearing plates to the connection board comprising at least one small clamping column and
urging or resilient bracing means arranged to be mounted at the end of said at least one clamping column for exerting on one of the bearing plates a thrust force in the direction of the connection board.
These pressure retaining devices apply quite particularly to electronic components, the connection of which to a connection board is effected by way of contact terminals. These contact terminals are arranged to co-operate with corresponding contact terminals located on the board to establish the electrical continuity. The electrical continuity between the contact terminals of the electronic component and of the board is obtained by simple mechanical pressure exerted on the electronic component in the direction of the printed circuit.
An electronic component provided with a plurality of contact terminals constituting an LGA (Land Grid Array) flat contact matrix is entirely suited to the employment of these devices, and will therefore serve as example in the continuation of this description.
The connection boards may be of all types of boards intended to receive electrical or electronic components such as printed circuit boards. Since printed circuit boards are particularly common, they will therefore serve as example in the continuation of the description to illustrate an embodiment of the invention.
Conventionally, an electronic component such as an integrated circuit is placed in a housing comprising contact terminals. In the continuation of the description, the expression xe2x80x9cLGA integrated circuitxe2x80x9d will be used to designate an LGA integrated circuit as well as a circuit placed in a housing.
Conventionally, the LGA integrated circuit has two faces, one active and the other inactive. The active face contains the contact terminals.
Generally, the connection of an LGA integrated circuit on a first face of a printed circuit board necessitates the use of a first bearing plate for exerting a pressure on the inactive face of the LGA integrated circuit and first clamping means for fixing or clamping the plate to the printed circuit board. The first clamping means comprise small columns intended to be fixed or clamped to the printed circuit board by means of inserts or nuts provided in the latter. The term xe2x80x9cfixingxe2x80x9d when used herein is intended synonymous with the words xe2x80x9cclampingxe2x80x9d or xe2x80x9choldingxe2x80x9d.
The mounting of a second LGA integrated circuit on the second printed circuit face, opposite to the first, also necessitates a second bearing plate and second fixing or clamping means which are respectively identical to the first bearing plate and to the first fixing means. The second fixing means are also fixed to the printed circuit board by means of inserts or nuts provided in the latter.
The drawback arising from this technique is that it is not possible to place, on each side of the printed circuit board and opposite each other, the fixing inserts or nuts necessary for the first fixing means and those necessary for the second fixing means. Thus it is not possible, with the known devices for retaining electronic components, to retain, by pressure, electronic components disposed opposite each other on each face of the same printed circuit board.
The invention aims to remedy this drawback by proposing a device for retaining by pressure two electronic components disposed opposite each other, each on an opposite face of the same printed circuit board.
The subject of the invention is therefore a pressure retaining device as described above, characterised in that, openings being formed in the connection board, said at least one clamping column is arranged to be mounted so as to be displaceable in translation in one of said openings in order to pass through the connection board and to receive the urging means at each of its ends, and in that it includes two fixing abutments for limiting the translation of said at least one clamping column through the connection board, said fixing abutments each being intended to be disposed on each side of the connection board, spaced from each other by a distance strictly greater than the thickness of the board so as to provide between the board and the abutments a clearance for balancing the retaining force between the two bearing plates.
The device described above makes it possible to retain by pressure at least two electronic components disposed opposite each other, each on a respective face of the same printed circuit board. In fact, in this device, the first and second bearing plates for retaining by pressure the electronic components are fixed to each other by way of small clamping columns passing through the printed circuit board from one side to the other. These plates are therefore no longer fixed by way of respective fixing means to the printed circuit board, and thus it is no longer necessary to provide inserts or nuts in the board.
According to other features of a pressure retaining device according to the invention:
said at least one clamping column includes two receiving means for receiving the fixing abutments and spaced from each other by a distance strictly greater than the thickness of the board, so as to provide between the board and the abutments the clearance for balancing the retaining force between the two bearing plates;
the abutments comprise a stop ring;
the abutments comprise a washer;
the urging means comprise thrust supports intended to be fixed to each end of said at least one small clamping column and resilient means arranged to be interposed between the thrust support and one of the bearing plates for urging the latter against the electronic components;
the resilient means comprise springs;
it includes a locking plate for locking said at least one clamping column in rotation and in which is formed an opening intended for slidingly receiving said at least one clamping column, the profile of the opening, and that of said at least one clamping column, being produced in such a manner as to prevent any rotational movement of said at least one clamping column relative to the bearing plates;
the first fixing means are arranged solely for fixing said bearing plates to the connection board;
it includes second fixing means for fixing a thermal energy dissipation radiator on at least one of said bearing plates, the second fixing means being independent of and separate from the first fixing means,
the second fixing means comprise a torsion clip arranged to bear against one of the bearing plates and the corresponding radiator.
A further subject of the invention is an electronic card, characterised in that it includes a device for retaining by pressure at least two electronic components disposed opposite each other and on each side of the same connection board, the retaining device being according to the invention.